Bad Egg

A Bad Egg in the party in Generation III

A Bad Egg (Japanese: ダメタマゴ Bad Egg), stylized as Bad EGG in Generation III, is a phenomenon present from the Generation III Pokémon games onward and in Pokémon HOME that results from a corruption of Pokémon data so that the checksum does not match up with the data's calculations. In Generation IV, sometimes Bad Eggs can hatch into ----- or another Bad Egg.

Bad Eggs are not really Pokémon Eggs, and may possibly never have been, but instead the default message returned by the game if the checksum is wrong (which happens only if data is altered badly). Bad Eggs rarely hatch and cannot be released, merely taking up space, though there are methods of removing them—it is possible to trade a Bad Egg away into another game, or remove it by cheating.

Game data

The Bad Egg's status screen in Pokémon Ruby and Sapphire

In Generation III, Bad Eggs appear with a type of ??? like a normal Egg, as well as have the same Pokémon status screen as an Egg would. Despite this, the similarities end there, as Bad Eggs can be holding items (such as Cherish Balls, which cannot be taken), be placed within types of Poké Balls aside from the standard kind, and have Seals attached—which prevents them from being deposited in the PC. After that, it is only possible to remove the seal from the Bad Egg by depositing it into the Pokémon Day Care. Some may be reported to have Pokérus or be cured of it, and may be fainted.

A Bad Egg placed in the first slot of the party will, rather than having a normal Egg menu sprite, have a differently colored version of the menu sprite of the Pokémon following it, such as a golden Bulbasaur, a blue Marowak, or a brown Ho-Oh. It is unknown exactly why the sprite retains the last Pokémon's sprite, but the color change is because of the use of palette 0 for this sprite—this is why Pokémon with palette 0 do not change color.

Being an Egg, it cannot be released.

If it is forced to hatch through use of a cheat code, a ? will come out and the game will immediately freeze.

From Generation IV onwards, a Bad Egg will be listed as being received on January 0, 2000, with the place received listed as the Mystery Zone.

Bad Eggs re-appear in Generation VI, not to be confused with 'mystery Eggs,' a glitch that is not fully related to Bad Eggs.

Game locations

Pokérus Bad Egg

In events

Evolution

Does not evolve Bad Egg  ???

Appearances of Bad Eggs

The Bad Egg's status screen in Pokémon Emerald

Generation III

When using the GameShark code for quick Day Care level-up, an invisible Bad Egg will appear in the party, which can be switched around using the PC and used in battle. Sometimes, the Bad Egg will take form of the silhouette of a Pokémon in the PC Box. However, attempting to view its summary screen will cause a game freeze, as shown in the video below.

Alternatively, by using codes to capture wild Pokémon instantly, reducing their HP to 0 yet keeping the battle going, it will be sent to the PC instead as a Bad Egg. This Bad Egg can be removed from the game by picking up another Pokémon while it is held, then setting it back down. This Bad Egg appears differently; instead of an Egg in its status box, it is the “unseen Pokémon” image used in the Pokédex and by ??????????. Like ??????????, using it in battle will cause an instant whiteout (if used without any other Pokémon in the party).

In Emerald, when warp cheat codes are used to steal from the Battle Factory, an invisible Bad Egg appears in the 19th slot of the 1st box in the PC Storage. If a Pokémon is in that slot, it corrupts the Pokémon and merges into a proper Bad Egg.

In Emerald only, the Battle Tower may be used to remove Bad Eggs. Should the player do these steps, and up to 4 Bad Eggs will be removed at a time. Required:

2 Pokémon

These 2 Pokémon must be different, preferably under level 50. They must be in the party while starting the glitch, and they can't be either an Egg or any of these:

Mewtwo

Mew

Lugia

Ho-Oh

Celebi

Kyogre

Groudon

Rayquaza

Jirachi

Deoxys

Up to 4 Bad Eggs

While starting the glitch, they must be in the PC.

Steps

1. Go to the Battle Tower.
2. Withdraw the Bad Eggs.
3. Save the game.
4. Deposit the Bad Eggs. Don't move other Pokémon.
5. Talk to the lady on the counter closest to the PC.
6. Soft reset the game before any of the “There is already a save file. Is it okay to overwrite it?” text appears.
7. The Bad Eggs should vanish.

In Pokémon Ruby and Sapphire, Pokémon FireRed, and Pokémon LeafGreen, it's impossible to get rid of Bad Eggs without trading them to Emerald first and doing the above steps.

Generation IV

Index number 495

The Bad Egg's status screen in Pokémon Diamond, Pearl, and Platinum

In addition to forcing an ordinary Pokémon to have an invalid checksum, it is possible to encounter a Bad Egg in the wild by using an Action Replay on Pokémon Diamond, Pearl, and Platinum and setting the wild Pokémon modifier code to 495 (an identifier of Manaphy Egg, although a Manaphy Egg is rendered as a Bad Egg in battle). The game will freeze instantly on capture when the game attempts to show the Pokédex entry, though some emulator versions allow it. A normal Egg captured this way (using an identifier of 494) will hatch into a random Pokémon, including Pokémon that do not normally hatch from Eggs like legendary Pokémon and evolved Pokémon, or may hatch into ----- or, like its Generation II counterpart, another Egg (which will then go on to hatch into a ----- itself). Due to being incorrectly generated, whatever is hatched may eventually turn into a Bad Egg itself, and then subsequently hatch yet again. The use of an Action Replay with a "1 hit kill" cheat in Double Battles will often result in a Bad Egg appearing. If the player sees a Bad Egg, the game will occasionally freeze. If Transform is used against a Bad Egg, its back sprite will be exactly the same as its front sprite and the only move it knows is Splash.

An Action Replay code can give the player a Bad Egg that is infected with the Pokérus, which will eventually hatch into a Shiny Rotom that is in Fan form.

From catching other Trainers' Pokémon via cheat

If the cheat to catch other Trainers' Pokémon is used, often the Pokémon caught, if following moving after another Pokémon, will either be named the same as the previous Pokémon, Bad Egg, or have a blank name. There are no other side effects.

Hacked data in Pokémon Battle Revolution

In Pokémon Battle Revolution, some Pokémon that are hacked may become Bad Eggs when they are copied from Diamond, Pearl, Platinum, HeartGold, and SoulSilver. A common example of a Bad Egg replacing a Pokémon is when that Pokémon has more than 510 effort values. Bad Eggs are unable to battle in Pokémon Battle Revolution.

If the player has a hacked Pokémon, although it won't appear to be a Bad Egg on a DS game, it will show up as a Bad Egg on Pokémon Battle Revolution if used in a DS battle.

Generation V

Generation V Action Replay code

In Generation V, if a wild Pokémon modifier code is used to encounter a Pokémon with a National Pokédex number greater than 649, a Bad Egg may appear as a result. The Egg will flee from battle. Catching the Egg will result in the message for a successfully caught Pokémon, but the data of the Egg will be deleted after the battle. The Egg does not have a Pokédex entry or any status information. The player's Pokémon will not earn any experience after the battle. Due to the removal of Seals as a game mechanic, Generation V Bad Eggs cannot have Seals.

Generation VI

	This glitch is in need of research. Reason: Are the Bad Eggs accessible as their own species like in Generation VI, and/or through corrupted Pokémon data? You can discuss this on the talk page.

Bad Eggs re-appear in Pokémon X and Y.^[1]

Generation VIII

In Pokémon HOME, Pokémon that are corrupted, altered with third party tools, or flagged by HOME's cheat detection can appear as Bad Eggs. They can't be imported into any HOME-compatible game, nor released, permanently taking up a box slot in the HOME account's storage. Obtaining a Bad Egg in Pokémon Sword and Shield or Pokémon Legends: Arceus and then attempting to launch Pokémon HOME with the Bad Egg in any Box slot results in HOME crashing.

From Max Raid Battles via ROM Hacks

In Pokémon Sword and Shield, Bad Eggs are possible to obtain through the use of ROM hacks, typically by changing the species Index number of a Pokémon that appears in a Max Raid to a value outside the range of valid IDs.

In both the summary screen and Max Raid Battles, the Bad Egg appears to be a Pikachu named "Egg", with a "black Poké Ball" as its sprite. Depending on the ID used, the model may appear as an actual Egg, despite behaving like a hatched Pokémon.

Prior to v1.2.1, it was possible for players with a ROM hack of Sword or Shield to distribute Bad Eggs to other players online (even to players playing unedited copies of the game online). This was done by hosting the edited Max Raid Battle through the Y-Comm, allowing up to 3 additional players to join it and capture the Bad Egg upon its defeat. Bad Eggs obtained via this method can be used for a cloning glitch involving the Pokémon Nursery: the "offspring" of a Bad Egg can be swapped with a party Pokemon, depositing the original into an empty box slot, while an identical duplicate appears in the party slot that the Bad Egg's offspring was swapped into.

Illegal moves, species, and forms in Legends: Arceus

In Pokémon Legends: Arceus, altering a Pokémon with third party tools to become a regional or alternate form that isn't coded into the game, a species that isn't coded into the game, or to include moves that are not in its moveset, will result in the Pokémon becoming an unhatchable Egg. This appears to be intentional feature, essentially acting as a built-in anti-cheat.

(Despite the lack of a Daycare or Nursery, Legends: Arceus does have a sprite for an Egg, which seems to be used exclusively for error handling when a valid sprite fails to load properly, or there is no valid sprite for that form or species.)

Generation IX

Main article: List of glitches (Generation IX) → Prior to v1.2.0 → February 27 to March 12, 2023 Poké Portal News Bad Egg

Main article: Poké Portal News → 2023 → February 27 to March 12, 2023

In other languages

This section is incomplete. Please feel free to edit this section to add missing information and complete it. Reason: Names in Generation VI

Language Title French Mauv. Œuf* Mauv. Oeuf* Mauv. OEUF* German Schl. Ei* Schl. EI* Italian Uovo peste* UOVO peste* Korean 불량알 Bullyang-al Spanish Huevo malo* HUEVO malo*

References

This glitch Pokémon article is part of Project GlitchDex, a Bulbapedia project that aims to write comprehensive articles on glitches in the Pokémon games.